// Protocol Buffers - Google's data interchange format
// Copyright 2008 Google Inc.  All rights reserved.
// https://developers.google.com/protocol-buffers/
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
//     * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

// TODO(kenton):  Use generics?  E.g. Builder<BuilderType extends Builder>, then
//   mergeFrom*() could return BuilderType for better type-safety.

package com.google.protobuf;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

/**
 * Abstract interface implemented by Protocol Message objects.
 *
 * <p>This interface is implemented by all protocol message objects. Non-lite messages additionally
 * implement the Message interface, which is a subclass of MessageLite. Use MessageLite instead when
 * you only need the subset of features which it supports -- namely, nothing that uses descriptors
 * or reflection. You can instruct the protocol compiler to generate classes which implement only
 * MessageLite, not the full Message interface, by adding the follow line to the .proto file:
 *
 * <pre>
 *   option optimize_for = LITE_RUNTIME;
 * </pre>
 *
 * <p>This is particularly useful on resource-constrained systems where the full protocol buffers
 * runtime library is too big.
 *
 * <p>Note that on non-constrained systems (e.g. servers) when you need to link in lots of protocol
 * definitions, a better way to reduce total code footprint is to use {@code optimize_for =
 * CODE_SIZE}. This will make the generated code smaller while still supporting all the same
 * features (at the expense of speed). {@code optimize_for = LITE_RUNTIME} is best when you only
 * have a small number of message types linked into your binary, in which case the size of the
 * protocol buffers runtime itself is the biggest problem.
 *
 * @author kenton@google.com Kenton Varda
 */
public interface MessageLite extends MessageLiteOrBuilder {

    /**
     * Serializes the message and writes it to {@code output}. This does not flush or close the
     * stream.
     */
    void writeTo(CodedOutputStream output) throws IOException;

    /**
     * Get the number of bytes required to encode this message. The result is only computed on the
     * first call and memoized after that.
     * <p>
     * If this message requires more than Integer.MAX_VALUE bytes to encode, the return value will
     * be smaller than the actual number of bytes required and might be negative.
     */
    int getSerializedSize();

    /**
     * Gets the parser for a message of the same type as this message.
     */
    Parser<? extends MessageLite> getParserForType();

    // -----------------------------------------------------------------
    // Convenience methods.

    /**
     * Serializes the message to a {@code ByteString} and returns it. This is just a trivial wrapper
     * around {@link #writeTo(CodedOutputStream)}.
     * <p>
     * If this message requires more than Integer.MAX_VALUE bytes to encode, the behavior is
     * unpredictable. It may throw a runtime exception or truncate or slice the data.
     */
    ByteString toByteString();

    /**
     * Serializes the message to a {@code byte} array and returns it. This is just a trivial wrapper
     * around {@link #writeTo(CodedOutputStream)}.
     * <p>
     * If this message requires more than Integer.MAX_VALUE bytes to encode, the behavior is
     * unpredictable. It may throw a runtime exception or truncate or slice the data.
     */
    byte[] toByteArray();

    /**
     * Serializes the message and writes it to {@code output}. This is just a trivial wrapper around
     * {@link #writeTo(CodedOutputStream)}. This does not flush or close the stream.
     *
     * <p>NOTE: Protocol Buffers are not self-delimiting. Therefore, if you write any more data to the
     * stream after the message, you must somehow ensure that the parser on the receiving end does not
     * interpret this as being part of the protocol message. This can be done e.g. by writing the size
     * of the message before the data, then making sure to limit the input to that size on the
     * receiving end (e.g. by wrapping the InputStream in one which limits the input). Alternatively,
     * just use {@link #writeDelimitedTo(OutputStream)}.
     */
    void writeTo(OutputStream output) throws IOException;

    /**
     * Like {@link #writeTo(OutputStream)}, but writes the size of the message as a varint before
     * writing the data. This allows more data to be written to the stream after the message without
     * the need to delimit the message data yourself. Use {@link
     * Builder#mergeDelimitedFrom(InputStream)} (or the static method {@code
     * YourMessageType.parseDelimitedFrom(InputStream)}) to parse messages written by this method.
     */
    void writeDelimitedTo(OutputStream output) throws IOException;


    // =================================================================
    // Builders

    /**
     * Constructs a new builder for a message of the same type as this message.
     */
    Builder newBuilderForType();

    /**
     * Constructs a builder initialized with the current message. Use this to derive a new message
     * from the current one.
     */
    Builder toBuilder();

    /**
     * Abstract interface implemented by Protocol Message builders.
     */
    interface Builder extends MessageLiteOrBuilder, Cloneable {
        /**
         * Resets all fields to their default values.
         */
        Builder clear();

        /**
         * Constructs the message based on the state of the Builder. Subsequent changes to the Builder
         * will not affect the returned message.
         *
         * @throws UninitializedMessageException The message is missing one or more required fields
         *                                       (i.e. {@link #isInitialized()} returns false). Use {@link #buildPartial()} to bypass this
         *                                       check.
         */
        MessageLite build();

        /**
         * Like {@link #build()}, but does not throw an exception if the message is missing required
         * fields. Instead, a partial message is returned. Subsequent changes to the Builder will not
         * affect the returned message.
         */
        MessageLite buildPartial();

        /**
         * Clones the Builder.
         *
         * @see Object#clone()
         */
        Builder clone();

        /**
         * Parses a message of this type from the input and merges it with this message.
         *
         * <p>Warning: This does not verify that all required fields are present in the input message.
         * If you call {@link #build()} without setting all required fields, it will throw an {@link
         * UninitializedMessageException}, which is a {@code RuntimeException} and thus might not be
         * caught. There are a few good ways to deal with this:
         *
         * <ul>
         *   <li>Call {@link #isInitialized()} to verify that all required fields are set before
         *       building.
         *   <li>Use {@code buildPartial()} to build, which ignores missing required fields.
         * </ul>
         *
         * <p>Note: The caller should call {@link CodedInputStream#checkLastTagWas(int)} after calling
         * this to verify that the last tag seen was the appropriate end-group tag, or zero for EOF.
         */
        Builder mergeFrom(CodedInputStream input) throws IOException;

        /**
         * Like {@link Builder#mergeFrom(CodedInputStream)}, but also parses extensions. The extensions
         * that you want to be able to parse must be registered in {@code extensionRegistry}. Extensions
         * not in the registry will be treated as unknown fields.
         */
        Builder mergeFrom(CodedInputStream input, ExtensionRegistryLite extensionRegistry)
                throws IOException;

        // ---------------------------------------------------------------
        // Convenience methods.

        /**
         * Parse {@code data} as a message of this type and merge it with the message being built. This
         * is just a small wrapper around {@link #mergeFrom(CodedInputStream)}.
         *
         * @return this
         */
        Builder mergeFrom(ByteString data) throws InvalidProtocolBufferException;

        /**
         * Parse {@code data} as a message of this type and merge it with the message being built. This
         * is just a small wrapper around {@link #mergeFrom(CodedInputStream, ExtensionRegistryLite)}.
         *
         * @return this
         */
        Builder mergeFrom(ByteString data, ExtensionRegistryLite extensionRegistry)
                throws InvalidProtocolBufferException;

        /**
         * Parse {@code data} as a message of this type and merge it with the message being built. This
         * is just a small wrapper around {@link #mergeFrom(CodedInputStream)}.
         *
         * @return this
         */
        Builder mergeFrom(byte[] data) throws InvalidProtocolBufferException;

        /**
         * Parse {@code data} as a message of this type and merge it with the message being built. This
         * is just a small wrapper around {@link #mergeFrom(CodedInputStream)}.
         *
         * @return this
         */
        Builder mergeFrom(byte[] data, int off, int len) throws InvalidProtocolBufferException;

        /**
         * Parse {@code data} as a message of this type and merge it with the message being built. This
         * is just a small wrapper around {@link #mergeFrom(CodedInputStream, ExtensionRegistryLite)}.
         *
         * @return this
         */
        Builder mergeFrom(byte[] data, ExtensionRegistryLite extensionRegistry)
                throws InvalidProtocolBufferException;

        /**
         * Parse {@code data} as a message of this type and merge it with the message being built. This
         * is just a small wrapper around {@link #mergeFrom(CodedInputStream, ExtensionRegistryLite)}.
         *
         * @return this
         */
        Builder mergeFrom(byte[] data, int off, int len, ExtensionRegistryLite extensionRegistry)
                throws InvalidProtocolBufferException;

        /**
         * Parse a message of this type from {@code input} and merge it with the message being built.
         * This is just a small wrapper around {@link #mergeFrom(CodedInputStream)}. Note that this
         * method always reads the <i>entire</i> input (unless it throws an exception). If you want it
         * to stop earlier, you will need to wrap your input in some wrapper stream that limits reading.
         * Or, use {@link MessageLite#writeDelimitedTo(OutputStream)} to write your message and {@link
         * #mergeDelimitedFrom(InputStream)} to read it.
         *
         * <p>Despite usually reading the entire input, this does not close the stream.
         *
         * @return this
         */
        Builder mergeFrom(InputStream input) throws IOException;

        /**
         * Parse a message of this type from {@code input} and merge it with the message being built.
         * This is just a small wrapper around {@link
         * #mergeFrom(CodedInputStream, ExtensionRegistryLite)}.
         *
         * @return this
         */
        Builder mergeFrom(InputStream input, ExtensionRegistryLite extensionRegistry)
                throws IOException;

        /**
         * Merge {@code other} into the message being built. {@code other} must have the exact same type
         * as {@code this} (i.e. {@code getClass().equals(getDefaultInstanceForType().getClass())}).
         *
         * <p>Merging occurs as follows. For each field:<br>
         * * For singular primitive fields, if the field is set in {@code other}, then {@code other}'s
         * value overwrites the value in this message.<br>
         * * For singular message fields, if the field is set in {@code other}, it is merged into the
         * corresponding sub-message of this message using the same merging rules.<br>
         * * For repeated fields, the elements in {@code other} are concatenated with the elements in
         * this message. * For oneof groups, if the other message has one of the fields set, the group
         * of this message is cleared and replaced by the field of the other message, so that the oneof
         * constraint is preserved.
         *
         * <p>This is equivalent to the {@code Message::MergeFrom} method in C++.
         */
        Builder mergeFrom(MessageLite other);

        /**
         * Like {@link #mergeFrom(InputStream)}, but does not read until EOF. Instead, the size of the
         * message (encoded as a varint) is read first, then the message data. Use {@link
         * MessageLite#writeDelimitedTo(OutputStream)} to write messages in this format.
         *
         * @return True if successful, or false if the stream is at EOF when the method starts. Any
         * other error (including reaching EOF during parsing) will cause an exception to be thrown.
         */
        boolean mergeDelimitedFrom(InputStream input) throws IOException;

        /**
         * Like {@link #mergeDelimitedFrom(InputStream)} but supporting extensions.
         */
        boolean mergeDelimitedFrom(InputStream input, ExtensionRegistryLite extensionRegistry)
                throws IOException;
    }
}
